DE2264962A1 - GLASS FABRIC WITH A COVER AND METHOD OF MANUFACTURING THE SAME - Google Patents

Description

Patent Attorneys Γν

Dr, Ing.Waiter Abftz Dr. Dieter F. Morf Dr. Hans-A. Browns

December 5th AD-il6l3-R / Div.I

P 22 25 W. 1 Tr.A. I.

E. I. DU PONT DE NEMORS AND COMPANY 10th and Market Streets, Wilmington, Del. 19898, V.St.A.

Glass fabric with a coating and method for making the same

The invention relates to polytetrafluoroethylene coatings on glass fabrics which are particularly suitable as pillows. Bag filters are commonly used to separate particles from flowing gases, either to collect them or to prevent environmental pollution in processes such as the production of cement and soot as far as possible. When working at high temperatures or with corrosive gases, glass fiber fabrics can theoretically be used, because glass has a relatively high melting point and chemical inertness. The use of glass fabrics for this purpose, however, is the fact that when the fabric is bent for the purpose, the

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separating the dust filtered off by the gas that has passed through it causes the glass fibers to break, so that the Tissue breaks and becomes unusable as a filter.

Various attempts have already been made with the glass fabric (either after processing the glass yarn into the fabric or before weaving) with a material that has the ability to withstand bending (flex life) of the glass fabric increased to cover. For example, glass fabrics with polytetrafluoroethylene or coated with silicone oil. According to another experiment, the glass fabric is first with one Ethylene oxide condensate or a polyethylene glycol fatty acid ester and then coated with polytetrafluoroethylene (U.S. Patent 3,090,701). According to CA-PS 577 68O this is Glass fabric with a coating of a solid dispersion of polytetrafluoroethylene in a butadiene / acrylonitrile copolymer Mistake. With these known coatings an improvement in the flexural strength of the glass fabric is achieved, however, further improvement is desired so that the life of the pilter tissue is increased, higher Temperatures are applicable and the filtration needs to be interrupted less often.

The object of the invention is a provided with a coating Glass fabric of improved flexural strength even after heat aging and production of such a coating a glass fabric.

The invention relates to a glass fabric with a coating which consists essentially of (a) unsintered polytetrafluoroethylene with a specific melt viscosity of at least 1 χ ίο "poise at 38O ⁰ C and (b) a condensation

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product of a polyhydrolyzable compound of tetravalent titanium, zirconium or tin, the components (a) and (b) in the coating either in the form of a mixture of (a) and (b) or as a basecoat from (b) and a top coat from (a) are present.

According to a special embodiment, the coating contains According to the invention, a water-repellent additive to prevent water from penetrating the fabric and mixes with the fine particles filtered off and clogs the holes in the tissue.

The coating consisting of the base coat and top coat can be produced by a two-step process by applying to the fabric a coating of a condensation product of a polyhydrolyzable compound of the tetravalent Titanium, zirconium or tin and then a top coat of polytetrafluoroethylene with a specific Melt viscosity of at least 1 χ ICr poise at 38Ο C brings up.

The coating consisting of the mixture of (a) and (b) can in a one-step process using a new coating compound and an aqueous dispersion of polytetrafluoroethylene, which contains the polyhydrolyzable compound, is applied. The coating compound may contain the water-repellent additive. Preferably the polyhydrolyzable compound is water soluble so that it is present in the form of a solution in the aqueous phase of the dispersion. The coating compound is applied to the fabric and then at temperatures at which condensation of the water-soluble compound is caused, but not

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are so high that sintering of the polytetrafluoroethylene caused is dried. A sintering of the polytetrafluoroethylene would worsen the flexural strength of the fabric.

The term "condensation product of a polyhydrolyzable compound" is descriptive of the sequence of reactions to which a compound of tetravalent Ti, Zr or Sn is subject. It is the ability of polyhydrolyzable Compound, first to be hydrolyzed, whereby it becomes condensable, and then a condensation, on which presumably the beneficial effect of the polyhydrolyzable compound according to the invention is due to be subject to. the So chemical composition of the polyhydrolyzable compound can vary over a fairly wide range, provided that only the compound is polyhydrolyzable.

More specifically, the polyhydrolyzability of the compound of tetravalent Ti, Zr and Sn means that the compound has at least two groups hydrolyzable by contact with water. Preferably the compound has of titanium, Zr and Sn at least three or four hydrolyzable groups.

Through the hydrolysis of the compounds of Ti, Zr and Sn, these compounds are converted into polyhydroxy compounds, for example by having hydrolyzate groups, halide or oxyhydrocarbon groups of the compound of Ti, Zr or Sn substitute. The hydroxy groups of the polyhydroxy compound

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make this condensable by splitting off water to form a condensation product with the recurring unit

t t

-M-O-M-O-,

I I

in which M is Ti, Zr or Sn and the remaining valences by hydrolyzable groups and / or hydrolysis products such groups and / or the same recurring unit alternating with the formation of a network structure M atoms and O atoms are saturated.

If heat is required to split off the water, the reaction can be called pyrolysis. Hydrolysis and Condensation can occur one after the other or, if this is noticeable, simultaneously. The identification the various stages of implementation are irrelevant. It is only necessary that the connection of Ti, Zr and Sn is subject to at least some condensation in contact with the glass fabric. That is, the condensation product is formed in situ on the glass surface of the glass fabric.

In general, the polyhydrolyzable compound of Ti, Zr or Sn is made from a liquid organic or

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aqueous medium applied to the glass fabric, with the choice of the medium depends mainly on the reactivity of the polyhydrolyzable compound, insofar as this is the target of formation of the condensation product influenced in situ. For example, some of the polyhydrolyzable compounds react with water even at low temperatures, for example room temperature, rapidly with the formation of an insoluble precipitate, presumably a product of both hydrolysis and condensation, after which the compound is no longer in a form in which it is suitable for application to the glass fabric. In such a case, the polyhydrolyzable compound must consist of a organic medium are applied to the glass fabric, a two-stage process for the formation of the coating according to the invention Procedure is applied. In some cases, although the polyhydrolyzable compound is reactive with water, it reacts that way slowly that an aqueous medium, including the aqueous polytetrafluoroethylene dispersion, can be used to the Apply compound before the reaction has taken place so far that a precipitate forms in the medium. In this If so, the one-step process for producing the coating according to the invention can be used. That is, a polyhydrolyzable one Compound that does not serve its purpose if it is applied from a certain medium, if in use Another medium can be used, and the choice of medium is decisive for whether the one-stage or two-stage Method according to the invention is applied. Regardless of the medium, the polyhydrolyzable compound should be in either be soluble or finely dispersible.

If the medium is organic, hydrolysis of the polyhydrolyzable occurs Connection after application to the glass fabric and removal of the organic medium. At this time contact with the water (steam) of the atmosphere with the dried compound leads to hydrolysis. In case of use an aqueous medium can hydrolysis at least up to one

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to some extent during storage of the coating medium or when heating the coating after it has been applied to the glass fabric for the purpose of evaporating the water. As well as when using an organic as well as an aqueous medium, the drying can be accompanied by warming to the To increase the drying rate or, if in the case of stable compounds, heating is necessary to promote hydrolysis and / or cause condensation. The temperature and time of heating are chosen so that the desired degree of condensation is achieved, but not so high that the polytetrafluoroethylene sinters in the coating.

If the hydrolyzable compound is water-soluble in the coating composition according to the invention, this means that it is soluble in water at 25 ^° C. in such concentrations that the flexural strength is considerably increased if it is in the corresponding concentration in the aqueous phase of the polytetrafluoroethylene dispersion is present. The water can contain a small amount of one or more organic compounds which are miscible with it and which are present in addition to the polyhydrolyzable compound in the form in which they are commercially available or which act as solubilizers that make the polyhydrolyzable compound soluble in water, contain. The degree of hydrolysis of the compound must be so low that the hydrolysis product in an equivalent amount of water at 25 ⁰ C does not precipitate out of solution so that the coating composition of the invention in which the hydrolyzable compound is dissolved, sufficient storage stability, pursuant. While the product of complete or substantial hydrolysis remains water soluble, the extent of hydrolysis and shelf life are not a problem. With the requirement that the hydrolysis product be water-soluble for at least an acceptable time, the hydrolyzable groups of the compound can be any groups which react with water under the conditions described. Examples of such groups are

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Halide and oxyhydrocarbon groups. The solubility of the In this embodiment, polyhydrolyzable compound in water means that the solution formed has the appearance of Has water.

"Polytetrafluoroethylene" is intended to mean (a) the aqueous dispersion (which is called fine powdery after coagulation and drying) of polytetrafluoroethylene, unless otherwise stated, derived from granular polytetrafluoroethylene used in the process according to the invention for increasing the bending strength of glass fabric cannot be used, and (b) the unsintered Polymer are understood.

The polytetrafluoroethylene used according to the invention has a high molecular weight, in contrast to polytetrafluoroethylene telomer, as is commercially available, for example, under the name Vydax Fluortelemor. Such a telomer has a number average molecular weight of about 2000 versus an average molecular weight of about 1 million or more for the polytetrafluoroethylene used in accordance with the invention. This higher molecular weight polymer differs from the telomer in toughness. For example, the telomer does not form a self-supporting film and has no measurable elongation. In contrast, the polytetrafluoroethylene used according to the invention has film-forming properties, and the resulting film or sheet, for example 0.0025mm (θ.1 mil) in thickness, is pliable and the polymer generally has an elongation in excess of $ 0% ( ASTM D-1457-69). In addition, the polytetrafluoroethylene used according to the invention is insoluble in all commercially available solvents.

The high molecular weight of the polytetrafluoroethylene used according to the invention results from its melt viscosity, which is an indirect measure of the molecular weight, the normal

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wise is not directly measurable is. The polytetrafluoroethylene has a melt viscosity (apparent melt viscosity) of at least 1 χ 1Cr poise at 380 ⁰ C under a shear stress of 0.457 kg / cm using the Schmelzindexmeßgerätes described in U.S. Patent No. 2,946,763. In contrast to copolymers of tetrafluoroethylene with other copolymerizable, ethylenically unsaturated monomers, such as hexafluoropropylene, this polymer is in sufficient quantities to keep the melt viscosity in a range, ie below 1 10 poise at 380 ^° C. below one

load of 0.457 kg / cm, which makes the polymer producible in the melt, not processable in the melt.

In the method according to the invention, as a source of the polytetrafluoroethylene component for the coatings according to the invention any commercially available aqueous polytetrafluoroethylene dispersion be used. The production of aqueous dispersions

Fluorine ions of high molecular weight polytetra & thylene are for example in U.S. Patents 2,559,752, 2,534,058 and 2,559,749. The method consists in adding tetrafluoroethylene to an aqueous solution of a polymerization initiator such as ammonium persulfate or disuccinic acid peroxide, and a dispersing agent such as an ammonium polyfluorocarboxylate having 7 to 10 carbon atoms with gentle stirring to avoid coagulation, presses in, so that an aqueous dispersion of colloidal Polytetraf luoroethylene particles with a particle diameter of, for example, less than 1.0μ and an average particle diameter of 0.10 to 0.30μ is generated. Dispersions in which the polymer particles are larger, for example an average diameter of at least 0.3M- have and that through in a certain way controlled addition of the dispersant to the polymerization medium as described in US Pat. No. 3,391,099 can, as well as that described in US Pat. No. 3,142,665 modified polytetrafluoroethylene in the Methods according to the invention can be used. The measurement of the particle size can be done by light scattering or by ultracentrifuge

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Technique can be carried out, as in the aforementioned US Pat. No. 3,391 described.

The condensation product present in the coating according to the invention is described in more detail below, initially with regard to the condensation products of tetravalent titanium, known as titania polymers can be referred to, and then with reference to condensation products of compounds of tetravalent Zirconium and tin. It is known that titanium oxide polymer Glass (U.S. Patent 2,768,909 and U.S. Patent 3,002,854) and polytetrafluoroethylene binds when separated from the vapor state. However, the titanium oxide polymer itself has only a small one Influence on the bending strength of glass fabric and polytetrafluoroethylene itself, therefore, results in only a negligible improvement which is offset by the cost of the polymer. Together with the polytetrafluoroethylene results in the titanium oxide polymer however, a surprisingly high improvement in the flexural strength of glass fabric. For example, a coating results according to the invention in many cases more than three times the bending strength of glass fabric compared to a glass fabric, which is covered with a coating of an equivalent amount of polytetrafluoroethylene alone. The coating of Fillers, such as glass fibers, with polysiloxane or condensed titanic acid ester with subsequent addition of these fillers an aqueous polytetrafluoroethylene dispersion is described in CA-PS 835 ^ 65. However, this patent specification does not apply to the production of coatings on glass fabrics, and even less, of course, the beneficial effect of such use described.

The titanium oxide condensation product preferred for the coatings according to the invention can be characterized as the product of a condensation of tetravalent titanium oxide units -TiO-, in which four oxygen atoms are bonded to each titanium atom.

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The condensation product is in sitty, i.e. after its Precursor called hydrolyzable organic titanate can, on the glass surface from an aqueous or organic Solution formed, i.e. after the titanium acid either as such or, if water-soluble, as part of it the aqueous polytetrafluoroethylene dispersion is applied. That Condensation product can be a simple linear product of the formula (RO) -, TiOTi (OR) ,, in which R is a hydrolyzable organic group, which can be replaced, for example, by hydrogen with formation of -OH, is sufficient, or a more complex one linear product as it is by the formula

RO

OA t

TiO OA

in which r is an integer of more than 1 or 2, R has the meaning given above and A is either R or H, or a fully hydrolyzed or even a crosslinked product in which some of the hydrogen atoms are replaced by titania units are replaced, and finally amorphous titanium dioxide, which probably has the following three-dimensional network structure:

I. - 0 1 - 0 - 0 0 0 - Ti - Ti I. - 0 T - 0 - 0 0 t t 0 - Ti - Ti I. I. 0 0 I.

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The amorphous titanium dioxide is the product of the final stage of a condensation of titania units and is produced by heating the hydrolyzable titanate or an incomplete condensation product obtained therefrom with removal (elimination) of water and / or organic groups present. The titanium dioxide pyrolysate is to be regarded as amorphous in the sense that in an X-ray analysis, in contrast to rutile and anatase, it is crystallographic Forms of titanium dioxide are not showing any crystallographic structure.

The condensation by which the various titanates present in the TiO ^ polymer component of the coatings according to the invention are present, formed: «rdei is complex and can be both a Hydrolysis as well as pyrolysis of the organic groups of the titanate precursor. With increasing degree of hydrolysis or pyrolysis, fewer and fewer organic groups are present, and the degree of polymerization of titanium oxide units increases. The final phase of the condensation takes place by pyrolysis with the formation of the network structure mentioned above.

The degree of condensation of the titanium oxide units in the titanium oxide polymer component can be so low that it cannot be detected by analytical methods. However, the degree of condensation can at a later stage, ie at the end use application of high temperatures of for example ⁰ C JOO increase. In the broadest sense, the titania polymer can be called the titania residue, which is dissolved by drying the

considered hydrolyzable organic titanate-containing mass arises, / will. With some highly active hydrolyzable titanates, such as Tetrabutyl titanate, by simply removing the organic solvent in which the titanate is soluble, the titanate is converted into Contact with air containing water vapor will hydrolyze.

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For some very stable titanates, such as titanium chelates, which do not hydrolyze significantly even when contained in ambient temperature water, it may be desirable to heat the titanate residue somewhat after the water has evaporated to cause some "degree of hydrolysis In the case of such titanates which are used as an aqueous medium, it is desirable that sufficient hydrolysis and / or condensation has taken place so that the titanate residue formed has become insoluble in water Heating to 150 ⁰ C for at least 1 minute can be achieved.

The titania polymer component can also be viewed as a derivative of ortho titanic acid, H ^ TiO ^, in which the hydrogen atoms are replaced by organic groups which give the resulting titanate the desired solubility and reactivity (hydrolyzability). For example, the selected organic groups are responsible for whether the titanate is soluble in water or in organic solvents and whether it is easily hydrolyzable and pyrolyzed. In any case, the organic groups are chosen so that they make the titanate hydrolyzable and condensable to amorphous titanium dioxide. With this requirement in mind, any hydrolyzable titanate capable of forming the titania polymer component of the coatings according to the invention can be used. Examples of such titanates are described in "Tyzor" Organic Titanates, publication D-4072 Rev. 3M 1070 from EI Du Pont de Nemours and Company. These titanates include the orthoesters and acylates of orthotitanic acid of the formulas Ti (OR ¹ ) or Ti (OCOR ¹ ) ^ (OR ¹ ), in which R ^{1 can be} alkyl, aryl or cycloalkyl, typically with 1 to 8 carbon atoms and ρ is an integer from 0 to 3. The titanium chelates, which are water soluble, can also be used. They are given by the formula Ti (OR) (OYXR in which R and ρ have the meaning given above, Y is a

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Carbon chain with 2 or 3 carbon atoms and X is oxygen or nitrogen, shown, wherein when X is oxygen, one group R and when X is nitrogen, two groups R are bonded. In all the above formulas, R can also be hydrogen to the extent that the subject compound, the acid would be Orthotitan-. Examples of hydrolyzable titanates are the tetraalkyl titanates, such as tetraethyl titanate, tetraisopropyl titanate and tetrabutyl titanate; Tetraethylene glycol titanate, triethanolamine titanate; Titanium acetylacetonatej titanium lactate; and the prepolymer which can be obtained by reacting tetraalkyl titanate with water. In the broadest sense, the titanate contained in the coating composition after application (before drying) is a titanate which condenses after drying (condensation of titanium oxide units), the condensation presumably taking place at least initially through hydrolysis of the titanate. As mentioned above, the number of titanate depends on whether water solubility is desired, as in the coating composition according to the invention, or whether a two-step process for producing the coating using an organic solvent for applying the organic titanate from a dispersion or solution is to be applied to the glass fabric.

The above discussion of the organic titanates and the titania polymer component of the coatings of the invention is generally applicable to zirconium as well. Ie organic compounds of this metal can be given by the formulas Zr (OR ¹ ) ^, Zr (OCOR ¹ ) ^ (OR ¹ ) and Zr (OR ¹ ) (OYXR ¹ ) ^ _, in which R ¹ , Y, X and ρ the have the meanings given above, are reproduced. Examples of such compounds are the tetraalkyl zirconates such as tetraethyl and tetrabutyl zirconate and the water-soluble chelates thereof. The condensation product of suitable organic compounds of zirconium contains the repeating unit

ι ι

-Zr -0- Zr-O-, in which the free valences are hydrolyzed by hydrolysing

Bare groups, hydrolysis products of such groups or the same repeating unit (bound via oxygen atoms) are saturated are, depending on the degree of condensation of the organic compound.

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Compounds of tetravalent tin which can be polyhydrolyzed with water can be organic or inorganic compounds, such as SnCl ₂ . The hydrolysis / condensation product of such tin compounds contains the recurring unit -Sn - 0 - Sn - 0 -,

r ι

in which the free valences by hydrolyzable groups, hydrolysis products of such groups or the same recurring Unit, which is bound via oxygen atoms, are saturated.

The glass fabric to which the coatings according to the invention are applied can be made of any glass, such as soda / lime / silica, aluminum silicate or borosilicate, but is usually the glass from which the commercially available glass fiber material (glass yarn) is made is. Typically, the glass fabric has a sizing agent, such as starch, on its surface. In contrast to previous experiences in the production of lubricant coatings on glass fabrics, the coatings according to the invention can be applied to the glass fabric provided with the sizing agent, which is referred to as "griege goods". If desired, however, the sizing agent can be removed from the glass fabric, for example by conventional heating, before the coating according to the invention is applied. For example, can be guided out of glass cloth through a heated to about 700 ⁰ C oven to burn off the Schliehtungsmittel for this purpose a web.

When the two-step method of applying the coating according to the invention is used, the polyhydrolyzable compound can by dipping, spraying or some other way of contacting the glass fabric with a solution or a dispersion of the compound in any concentration, depending on the amount to be absorbed by the glass, to the Glass can be applied. The medium can either be an organic solvent or water, depending on the solubility of the Compound in this medium and the reactivity of the compound with the medium. Examples of organic media that act as solvents can be used are isopropanol, n-heptane,

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Trichlorethylene, tetrachlorethylene, n-butanol, benzene, isopropanol / Water, methyl ethyl ketone and Stoddard solvent. If the Polyhydrolyzable compound is insoluble or becomes insoluble in water, a solution of the compound in an organic Solvent, which in turn is soluble in water, can be produced. For example, titanium acetylacetonate is in isopropanol, but not soluble in water. If glacial acetic acid is first added to the solution of the titanate in isopropanol, the resulting solution decreases Solution water when it is slowly added with stirring so that an aqueous solution is obtained. The polyhydrolyzable Compound and the solvent are chosen so that no undesirably strong hydrolysis of the compound takes place until the coating is heated to evaporate the liquid medium. Titanates, which react with water at ambient temperature, are such as tetrabutyl titanate, used in the form of a solution in an organic solvent. Polyhydrolyzable compounds, which are soluble in water but do not react appreciably with water at ambient temperature, such as titanium lactate and cJ-Aminoalkyltrialkoxysilane can also be used as an aqueous solution will. The hydrolyzability of some of the compounds is retained even when the compound is in an aqueous medium is resolved. After the coating has been applied to the glass fabric, the solvent is removed by drying with or without the application of Heat is removed from the condensation product on the glass fabric to form the desired layer.

When using the two-stage process for applying the coating, after the base coat of the polyhydrolyzed compound or its condensation product has dried, the stage of applying the top coat of polytetrafluoroethylene takes place. The polytetrafluoroethylene content of the dispersion can have any desired value depending on the desired thickness of the coating. The double-coated glass is then dried. The drying temperature should not be above 300 ⁰ C, so that no sintering of the polytetrafluoroethylene takes place,

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whereby the flexural strength of the fabric would suffer.

If the whole coating is applied in a single step, is the polyhydrolyzable compound in the aqueous polytetrafluoroethylene dispersion srfchalten, and this dispersion is applied to the glass and then dried (however the polytetrafluoroethylene is not sintered), so that a coating from which polytetrafluoroethylene is formed in admixture with the condensation product of the invention. This mixture is not necessary a uniform mixture, because presumably during the evaporation of the aqueous phase of the dispersion a considerable Part of the dissolved compound migrates to the glass surface, so that the resulting coating is exposed at its Finally, the surface is rich in polytetrafluoroethylene.

When using the one-step process for applying the entire coating according to the invention, a coating composition are used in which the polyhydrolyzable compound added to the aqueous polytetrafluoroethylene dispersion in water is soluble.

Both when using the one-step and when using the two-step process, the total thickness of the coating depends on the desired use of the glass fabric provided with the coating. Use to filter a flowable, abrasive medium generally requires relatively thick coatings in order for the fabric to have a long service life. For many uses, only a thin coating is required to give the glass fabric improved flexural strength _; and an advantage of applying excessively thick coatings is outweighed by a reduction in permeability and difficulty in handling the fabric, as well as the cost of such a coating. In any case, the

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Holes in the fabric between the yarns that make it up is not closed by the coating. Good results are generally obtained when a coating is used in a one-step or two-step process in an amount of

1 to 80 g / m of glass fabric surface (1 side) and usually 1 to 60 g / m, expediently 15 to βθ g / m, and more optimally to achieve this Results 15 to 45 g / m is applied, the amount of coating also depends on the glass fabric to be provided with the coating.

Both application of the single stage and the two stage process for the preparation of the coating does not consist of the coating generally necessary, however, from 50 to 99 * 5 wt .- ^ of the polytetrafluoroethylene and from 0.5 to 50 wt -.% Of the condensation product the polyhydrolyzable compound (which compound is believed to be the condensation product). The coating preferably contains at least twice as much polytetrafluoroethylene as the condensation product. Weight of the components present therein and the coating weight per cent (hereinafter referred to as dry weight) after heating the dry coating for 10 minutes at 150 ⁰ C determined. When using the two-step process, the condensation product is usually in its own (intermediate) layer separate from the polytetrafluoroethylene, although the top layer may also contain some condensation product. When using the one-step process, the coating consists of a mixture of both components.

That used for the manufacture of the coatings according to the invention aqueous polytetrafluoroethylene dispersion generally contains

2 to 70 ^ polytetrafluoroethylene, based on the weight of the Polytetrafluoroethylene plus water, and a sufficient amount of water-soluble (dissolved) polyhydrolyzable compound with it the above-mentioned content of condensation product in the coating is achieved from the mixture. I.e. the concentration on the

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The polyhydrolyzable compound added to the dispersion can range from $ 1 to $ 70 based on the weight of what is present Polytetrafluoroethylene. Preferably there is at least twice as much polytetrafluoroethylene as polyhydrolyzable Compound present in the dispersion. Since the condensation product weighs less than the polyhydrolyzable compound for At the time of their addition, these masses dry to the desired coating.

Even if the methods for making the coating according to the invention above are considered to be one-step (one coating) or two-step (two coatings) are designated, it is also possible, in each of these embodiments, some coatings of the same Apply component to the desired coating thickness reach.

According to the invention, the glass yarn as such can also be provided with the coating, the coating composition according to the invention is expediently applied in the manner described above in connection with a glass fabric, and then the yarn to be processed into the fabric.

According to another embodiment of the invention, the aqueous Polytetrafluoroethylene dispersion either when using the one-step or the two-step process for the preparation of the Coating a small amount of a compatible water-repellent additive added so that after the coating has dried on the glass fabric water condensate does not spread over the surface of the glass fabric or along the yarn of the fabric penetrates into this if this is the first time with containing pesticides hot gas is brought into contact, which can cause clogging of the tissues. To this end any additive that is soluble or dispersible in water and capable of rendering the fabric hydrophobic can be used.

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The additive does not have to have the thermal resistance of the coating itself and can be burned by the hot exhaust gases, because, once the glass fabric has been heated to above the boiling point of water, no more condensation of water vapor can take place. Usually, with an addition of from 0.1 to 10 $ based on the weight of the polytetrafluoroethylene in the coating or in the new coating mass' according to the invention, the fabric a sufficient Hydrophobicity conferred, but in principle any amount can be used with which the purpose is achieved without that the tissue is damaged. The amount required to achieve this result varies with amount and Type of that present in the aqueous polytetrafluoroethylene dispersion surfactant. Usually such a dispersion contains 1 to 15 surfactant, which is usually is anionic or nonionic based on the weight of the polytetrafluoroethylene in the dispersion.

The surface-active agents added to the dispersion are soluble in the desired concentration in water at room temperature (20 to 25 ^° C.). Examples of surface active agents are the reaction products of ethylene with other compounds which impart hydrophobic components to the surface active agent, such as propylene oxide, amines, saturated and unsaturated alcohols and acids and alkyl phenols. Other suitable surface-active agents, which are not obtained by reacting with ethylene oxide, but can also be used in the aqueous polytetrafluoroethylene dispersions used according to the invention, are the alkanolamides and the fatty acid esters, such as the methyl esters of caprylic, caproic, stearic and oleic acid. Some of the surfactants described above correspond to the following formulas:

0 (E) H

-20 ~

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in which E _{n is} the group (" ^C 2 ^H 4 ° ~) _U ^or a mixture of the groups (-C ₂ H.0-) _a and (-C-AjO-) _b , where η is in each case an integer of 2 to 50 and preferably 2 to 18, b is an integer

from 0 to 30 and a is an integer of at least 2, a and

ρ b are η, u is an integer of 1, 2 or 3 and R is an aliphatic saturated or unsaturated, straight-chain or branched or cyclic hydrocarbon group having generally 8 to 2Λ, preferably 8 to 18 carbon atoms

ρ
is, is. Examples of groups R are oleyl, stearyl, tridecyl, lauryl, decyl and the groups which are derived from aliphatic glycols and triols;

in the G the group (-CpH ^ O-) or a mixture of the groups

and (-

in each case a whole

Number from 2 to 50, preferably 8 to 20, d is an integer of 0 to 30, c is an integer of at least 2 and c plus d is m; R ^ a monovalent aliphatic straight chain or branched and usually saturated aliphatic hydrocarbon is a group having 4 to 20 and preferably 8 to 12 carbon atoms;

RN Γ (CH ₂ CH ₂ O) H

and

R-CON

(CH ₀ CH ₀ O) ₀ H.

in which q is an integer from 2 to 50, t an integer from

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1 or 2, R is a chemical bond to a group (CH ₂ CH ₂ O) H, when t is 2, and an alkyl group having 1 to 8 "carbon atoms, when t 1 is an alkyl group having 1 to 8 carbon atoms, Fr, , with the proviso that Br plus R contain at least 6 carbon atoms; the polyalkylene oxide block polymers of the formula:

HO (C ₂ H ₄ O) ₈ (C ₃ H ₆ O) _f (C ₂ H _{4 O) 6} H.

where f is an integer from 15 to 65 and e and g are integers large enough that e plus g together make up 20 to 90 $ of the total weight of the polymer. For each of the surface-active agents of the formulas given above, the parts and the molecular weight of the hydrophobic and hydrophilic portions are such that the above requirement for water solubility is satisfied. Other special surfactants are:

(CH, (CH ₂ ) ^ CH ₂ (OCH ₂ CH ₂ ), OH; CH ₃ (CH ₂ J ₆ CH ₃ (OCH ₃ CH ₃ J ₃ OH;

CH (CH ₂ J ₈ CH ₂ (OCH ₂ CH ₂ J ₁₀ OHu CH ^ (CH ₂ J ₈ CH ₂ (OCH ₂ CH ₂ J ₅ OH and

I ₂ CH ₂ ) ₁₀ (

V (OCH ₂ CH ₂ J ₁₀ OH.

The water-repellent additives are generally available commercially under the name Zepel and Scotchgard. These agents are polymers of fluorinated esters of acrylic acid, including methacrylic acid (fluorinated acrylate polymer). The fluorinated portion of the ester group is generally in the form of a perfluoroalkyl group having from J> to 12 carbon atoms. The polymers can be homopolymers or copolymers, including segmented ones

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ORIGINAL BATHROOM 50 9 8 L? / 093 y

AD-4613R / ^D iv.lt ^

Copolymers with other copolymerizable monomers, wherein the repeating ester unit, which is responsible for the water repellency of the polymer, generally by the formula

CH ₂ - CJ

in which J is H or CH ^, s is an integer from 1 to 12 and Q is a organic group representing a perfluoroalkyl group with 3 to 12

is,

Contains carbon atoms / can be represented. Examples of monomers, of which this repeating unit is formed during polymerization (or copolymerization) are:

CH ₂ = CHCOOCH ₂ (CFG) GCF

CHg = CHCOO CHg (CFg) ₄ CF ₃

CH ₂ = CHCOOCHg (CFg) g CF ₃

CHg = CHCOO (CHg) ₁₁ (CFg) ₇ CF ₃

CHg = C (CH ₅ ) COOCHgCHgN (CH ₃ ) SOg (CFg) ₇ CF ₅

CHg = CHCOOCH ₂ CH ₂ N (CHgCHgCH ₃ ) SO ₂ (CFg) ₇ CF ₃ and

CHg = C (CHg) COOCHgCH ₂ (CF ₂ ) CF ₃ .

These water repellent additives are in some organic solvents soluble and are generally in the form = one aqueous dispersion, that of the aqueous polytetrafluoroethylene dispersion can easily be added to form a codispersion. More examples of water-repellent additives are in U.S. Patents 2,642,416, 3,068,187, 3,102,103, 3,256,230, 3 256 231, 3 277 039, 3 378 609 and 2 803 615.

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The following examples illustrate the invention. Data in parts and percent relate to weight, unless otherwise stated. The following procedures and materials were used unless otherwise specified.

The test for bending strength of glass fibers in the form of fabrics is the MIT bending test, which is carried out as follows: The apparatus used is an MIT Folding Endurance Tester manufactured by the Tinius Olsen Testing Machine Company. It is be essentially of a pair in a spaced-apart clamping jaws for gripping the opposite ends of a pattern of a glass cloth. The machine works to repeatedly fold and bend the pattern around a bend line through an angle of 270 °. The flex life of the specimen is the number of double folds (two folds correspond to one cycle) that the specimen passes before it breaks. During folding is one of the jaws by a predetermined constant load 908-2070 g against the other inclined (biased), and when the sample breaks, the loaded clamping jaw of the other moved away, from which it is seen that the test is completed. For each type of glass fabric, three samples are tested and the flexural strength reported is the mean of the three runs. The glass fabric sample is cut out of larger samples of the glass fabric with a die, and each sample is 7 * 61 cm in length in the direction of the warp threads and 1.27 cm in width in the direction perpendicular thereto. That is, unless otherwise stated, the bending strength of the warp threads is tested. At each end of the pattern, an adhesive strip is applied there on both sides where the pattern is gripped by the jaws so that it can not slide within the jaws during the test.

Heat resistance (heat aging) is measured by using the

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Heated pattern of the glass fabric in a Luftzugofen for 40 hours at 280 to 315 ⁰ C and then the MIT bending test subjects the pattern.

The resistance of the glass fabric against acid vapor is tested by heating the sample in a closed vapor chamber 100 minutes via a to reflux (about 100 ⁰ C) sulfuric acid aqueous solution of 35 wt .- # suspended and then the MIT bending test subjects.

The aqueous polytetrafluoroethylene dispersion used in the examples contained polytetrafluoroethylene particles with a mean diameter of 0.2βμ, the particles predominantly Spheroids were. The dispersion contained 6.0 wt% Triton X-100 as a nonionic dispersant that is believed to have the formula

(0CH ₂ CH ₂ ) ₁₀ 0H)

Has. The polytetrafluoroethylene in the dispersion had a

Melt viscosity of about 10 poise at 380 ⁰ C under a shear

load of 0.457 kg / cm

The titanium acetylacetonate used in the examples is the reaction product of 1 mole of tetraisopropyl titanate and 2 moles of acetylacetone. The titanium lactate used in the examples is this neutralized (ammonium) reaction product of 1 mol of tetraiso-propyl titanate and 2 moles of lactic acid.

The glass fabrics A, B and C used in the examples have the following properties:

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Medium permeability,

TL ρ

mVinin per m

Weight, g / m

fc'adenzahl, weft threads / cm (Thread count picks / in.)

tissue

chain

Fill yarn

Glass fabric A. B. 12th
30th C. 12th
30th 4.5-6.0 23.5 1/2 10.5 1/2 298 310 520 21 χ 20
54 χ 52 21 χ
54 χ 20 x
50 χ Crow's foot
(crowfoot)
150's 1/2 twill
150's twill
150's

bulked 1/4 bulked 1/4

example 1

A. A stock solution of nydrolysierbarem titanate was prepared by mixing 4 parts were added to a solution of 75 $ titanium acetylacetonate in isopropanol with 8 parts of glacial acetic acid and this mixture was added dropwise 88 parts of distilled water was added so that a substantially aqueous solution of the titanate was obtained.

B. The fabric treated in this example was through heat-cleaned glass fabric Q and the load used in the MIT bending test was 2070 g. The coating was applied by dipping the fabric into the coating solution or dispersion and then passing the fabric provided with the coating between nip rollers of a wringer and then drying ^{at 150 ° C. for 10 minutes.}

C. In one trial, the heat-cleaned fabric was subjected to the MIT bending test with no coating on the fabric. The flexural strength of this fabric was 123O cycles.

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D. In another experiment, the heat-cleaned tissue was coated with the titanate stock solution. The MIT bending test gave 1090 cycles for this specimen, indicating that no improvement in flexural strength is achieved with the titanium oxide polymer coating alone.

E. In a further experiment, the heat-cleaned fabric was treated with an aqueous polytetrafluoroethylene dispersion (6 $ Polytetrafluoroethylene solids) coated so that the fabric had a polytetrafluoroethylene coating of 33.5 g / m (dry weight). The MIT bending test gave a value of 35 ^ 0 cycles.

P. The experiment of Part E of this example was repeated except that the one coated with the titania polymer Fabric from Part D of this example was used. The glass fabric obtained, which has both a coating of the titanium oxide polymer as well as a top coat made of poly te met luoroethylene with a total weight of 36 g / m (dry weight), resulted in im MIT bending test has a bending strength of 8200 cycles.

Example 2

375 ml of the titanate stock solution from Example 1 were mixed with 375 ml an aqueous polytetrafluoroethylene dispersion (60 $ polytetrafluoroethylene solids) mixed, and the mixture was diluted with distilled water in individual portions so that Heat-cleaned glass fabric C with coatings of various weights obtained after drying by the method of Example 1 became. The results of the MIT bending tests are summarized in Table I:

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T a b e 11 e

coating (dry weight) bending test, cyclen

K / n ² 2070 R load 52.5 io 890 39.5 9 890 28.8 8 960 16.5 9 010 5.5 4,220 1.9 2 720

This series of tests shows the increase in the bending strength by applying a coating consisting of a mixture on the fabric. With the lowest coating weight (1.9 g / m), d approximately the weight of the titania polymer coating of Part D of Example 1 corresponds to more than twice the flexural strength achieved. With a coating weight of 28.8 g / m 2, the flexural strength was more than twice that with a coating weight of 33 * 5 g / m, if the coating consisted of polytetrafluoroethylene alone, as indicated in Part E of Example 1.

Mixtures of the titanate stock solution were used for comparison of Example 1 prepared with aqueous dispersions of various other polymers, and purified by heat Glass fabric C was provided with coatings made from these mixtures and dried, after which the MIT bending test was carried out at a load of 2070 g. The details of the experiments were: In one experiment the mixture consisted of 50 ml of titanate stock solution and 50 ml of an aqueous dispersion of poly (tetra-

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fluoroethylene / hexafluoropropylene) (about 1β $ hexafluoropropylene in the copolymer and 55 $ solids in the dispersion). The weight of the coating was 50 g / m (dry weight) and the MIT flex test gave J54-10 cycles. In a further experiment, the copolymer dispersion from the previous experiment was replaced by an aqueous dispersion of polyethylene. The weight of the coating was 27.5 g / m (dry weight). The MIT flex test gave 1630 cycles. In a further experiment, the titanium oxide polymer coated fabric of Part D of Example 1 was coated with a polytetrafluoroethylene telomer _{of molecular weight 2000 contained in Cl 2 CPCF 2} Cl, so that the telomer weight on the fabric was about 48 g / m (Dry weight). The MIT flex test gave 2700 cycles.

Example 3

In this example, the glass fabric C was used either after heat cleaning or untreated (greige goods), presumably coated with starch as a sizing agent. The tissue samples were first immersed in a solution of titanium acetylacetonate 2.25 $ 0.75 $ isopropanol, methyl ethyl ketone and dipped 6 $ 91 $ HPO and then passed through a wringer and dried for 10 minutes at -150 ⁰ C. Then, a top coat was applied from polytetrafluorethylene, by dipping the fabric in an aqueous PoIytetrafluoräthylendispersion and then passed through a wringer, and dried at 150 ⁰ C. By diluting the aqueous dispersion with distilled water to a polytetrafluoroethylene content of 20, 10 and 5%, polytetrafluoroethylene coatings of various weights were obtained on the fabric. The obtained coated glass fabrics in a two-step process were subjected to the MIT bending test (load 908 g), and the heat resistance and resistance to acid vapor were determined. Details of these experiments and their results are given in Table II.

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T a b θ 11 β II

State of the

cn ο co it

O ι

template Glass mix Polytetra
fluoroethy-
len a heat cleaned 48.5 a not heatable 48.5 b heat cleaned 25th b not heatable 25th C. heat cleaned 12.5 C. not heatable 12.5

coating (dry weight) g / m

TiO ₂ polymer

MIT Blegetest - Cyclen

originally

7100 22800

.6400 I85OO

3700 10900 '

exposed to heat-acid aged

10800 50 100

4300 257OO

96OO

192OO

225OO

38OO 14500

10500

AD-4613R / Div. I.

All of these results show the improvement in bending strength compared to heat-cleaned, non-coated glass fabric, which in the MIT bending test has a bending strength of 1230 cycles. These results also show that the fabric provided with sizing agent has a better flexural strength than glass fabric cleaned with heat, if it is provided with a coating according to the two-step process according to the invention. In addition, the coating has a good resistance to heat and acid vapors and in some cases shows improved flexural strength. In trade available glass fabric C, which is covered with a top coat of polytetrafluoroethylene, Silicone oil and graphite, showed a bending strength of only 1400 in the MIT bending test Cyclen.

Example 4

The same two-step process was used in this experiment as in Example 3 with the difference that the titanate stock solution 3.7 ^ des titanate, 1.25 $ isopropanol, 10 $ methyl ethyl ketone and contained $ 85 water. By diluting the aqueous Polytetrafluoroethylene dispersion with distilled water to a polytetrafluoroethylene concentration of 10 $ was used as a coating with 18.2 g / m polytetrafluoroethylene and 8.1 g / m titanium oxide. polymer (both dry weight) obtained. The fabric with the applied in two stages. Coating had an original bending strength of 38ΟΟ Cyolsn in the MIT bending test heat-cleaned tissue and 15 ^ 00 cycles where not heat treated fabric. After "treatment with acid steam the heat-cleaned fabric had a bief in the MIT bending test. Resistance to 5900 cycles and that not treated with heat The sample has a bending strength of 12 200 cycles. The results of this experiment are comparable to those obtained with samples b of Table II, in which the aqueous polytetrafluoroethylene dispersion also up to 10 $ polytatrafluor

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Ethylene was diluted, comparable. The lower concentration of titanium oxide polymer gave better results in these samples.

Example 5

In this series of experiments, 100 parts of the titanate storage solution from Example 3 were added to 50 parts of aqueous polytetrafluoroethylene dispersion (60 ^ polytetrafluoroethylene solids), and the dispersion thus obtained (sample a) was first mixed with 100 parts of water (sample b) and then with a further 100 parts of water ( Sample c) thinned. The glass container C, both heat-resistant and not heat-treated, was immersed in the dispersions obtained and then passed through a wringing device and ^{heated to 150 °} C. for 10 minutes. The details of these tests and the results of the MIT bending test (load 908 g) are summarized in Table III.

T a b e 11 e

III

State

Mu- des glasster fabric

Cover ₂ (dry weight)

... MIT bending test Cyclen

Polytetra- TiO ₂ -PoIy- original thermal acid fluoroethylene mer borrowed aged a

heat cleaned

not heat treated

warmer.

not heat treated

warmer.

not heat · beh.

41

7.5

41 , 2 7.5 21st , 2 5.1 21st ,8th 5.1 11 5.6

11.8

5.6

78OO 27 3OO 20 6OO

40 700 21 500 33-500

9 300 8 6OO 9 400

23 400 21 800 11 800

7 600 9 000 5, 900

15 900 23 800 15 400

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In the cases of Examples 3 and 4, the bending strength was the coated, non-heat-cleaned fabrics better than that of the coated heat-cleaned fabrics Tissue.

Example 6

In this experiment, 100 parts of the titanate stock solution were used of Example 4 to 20 parts of an aqueous polytetrafluoroethylene dispersion (605 & Polytetrafluoräthy1en) added so that a Coating of a mixture of 20 g / m polytetrafluoroethylene and 6.2 g / m titanium oxide polymer (dry weight) on the in Example 5 was obtained. The MIT bending test (Load 908 g) of the coated heat-cleaned The fabric gave 10,200 cycles and that with the coating provided, non-heat-cleaned fabric 24,300 cycles.

Example 7

In this example heat-cleaned glass fabric A was used, and the MIT flex test was performed with a load of 18Ϊ6 g carried out. The following solutions of titanate in an aqueous polytetrafluoroethylene dispersion were prepared:

A. Coating compound G D. 1
Component, g B. aqueous polytetrafluoro- 400 400 200 Ethylene dispersion 2 177 400 80 116 Titanate solution ^ 354 115 I60 16 Glacial acetic acid 666 .230 96Ο 176 Water (distilled) 855

1. The ingredients were made by adding acetic acid the titanate solution and then added dropwise added so much water that the aqueous solution obtained could be mixed with the aqueous dispersion,

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and then added more water to give the desired coating weight. 2. 60 # polytetrafluoroethylene

Titanium acetylacetonate and 25 # isopropanol.

Samples of the glass fabric were dipped into the dispersions and then passed through a wringing device and ^{dried at 200 °} C. for 4 minutes. The details of these tests and the results of the MIT bending tests are shown in Table IV.

509842/0938 - 3 * -

VJI Coating
Dimensions Ratio polytotra- T a b e 11 θ IV Bending test - Cyclen acid
selected ü
σ \ I. A. fluoroethylene to TiO ₂ -
polymer (dry weight) Total coating original
lich warming
ages 2012 Sd
α
Η · B.
C. 1.8 / 1.0 (Dry weight,
g / m ² ) 1334 959 938
873 H D. 2.8 / 1.0
4.0 / 1.0 15.6 1129
939 1647
1936 1275 5CS8 20.0 / 1.0 15.6
15.6 878 1187 ro 15.6 093 8

K) NO CD

AD-4613R /Div.I

In all cases, according to the MIT bending test, the heat-cleaned, Uncoated glass fabric A (94 cycles) achieved at least about 20-fold improvement. If this series of tests is repeated, with the difference that the fabric is covered with a different coating from the dispersion was provided so that a coating of 30 g / m 2 was obtained, an even further improvement in the bending strength according to the MIT test was achieved.

Example 8

The procedure of Example 7 was repeated with the mass D with the difference that less water was used and the Composition 5 * 5 $ of an aqueous dispersion of fluorinated acrylate polymer ($ 14 polymer solids), more specifically, the mixture of fluorinated and non-fluorinated polymer emulsions of Example VII of U.S. Patent 3,378,609. The weight of the The coating on the glass fabric was 36 g / m 2 and the MIT bending test (1816 g load) of the fabric gave 3792 cycles and after heat aging and acid treatment 48o8 and 2721 cycles, respectively. When this procedure was repeated except that the acrylate polymer was omitted, a coating of the of the same weight in the MIT bending test, a bending strength of 3842 or 5939 and 2902 cycles. These results show that the water-repellent additive does not adversely affect the flexural strength of the glass fabric.

Example 9

In this example, a sample of heat-cleaned glass fabric A was dipped into an aqueous polytetrafluoroethylene dispersion (35 ^ polytetrafluoroethylene), passed through a wringer and ^{dried at 150 °} C. for 10 minutes. The coating on the sample obtained in this way had a weight of 31 g / m 2 and in the MIT bending test (2070 g load) a bending strength of 1340 cycles was determined. When this experiment is repeated with the difference that in the dispersion

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Λ% titanium acetylacetonate (added as ^ stock solution from Example 1), based on the total weight of the dispersion, was dissolved, the MIT bending test showed a load capacity of 72βθ cycles.

Example 10

200 g of aqueous polytetrafluoroethylene dispersion were diluted with 1.54 g of distilled water to a polytetrafluoroethylene content of 355%. 250 g of this diluted dispersion were mixed with 250 g of the titanate stock solution from Example 1. This mixture was further diluted with 1300 grams of distilled water so that the resulting dispersion contained about 5% polytetrafluoroethylene solids. A piece of heat cleaned glass fabric C was immersed in this mass, so that a coating was obtained with a weight of about 35 * 8 g / m ² after four minutes drying at 205 ⁰ C. The MIT bending test (908 g load) of the glass fabric showed a bending strength of 8246 cycles.

Example 11

200 g of an aqueous polytetrafluoroethylene dispersion (60% polyte met luorä thy I en) were diluted with 13 ^ · S distilled water. 250 g of an aqueous solution of titanium lactate obtained by diluting 18 g of a 50% aqueous titanium lactate solution with 282 g of distilled water were added to 250 g of this diluted dispersion. 1,500 g of distilled water were added to the dispersion obtained in this way. Heat-cleaned glass fabric swatches C were immersed in this dispersion and dried at 205 ° C. for 4 minutes, so that a mixed coating on the glass fabric of 26 g / m 2 (dry weight) was obtained. The MIT bending test (908 g load) showed a bending strength of 11 128 Cyeles.

Example 12

20 g of a 50% aqueous titanium lactate solution and 2180 g of distilled water were added to 200 g of aqueous polytetrafluoroethylene dispersion (60% polyte met luorä thylen). Warmth-

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Cleaned glass fabric C was immersed in the dispersion obtained in this way and ^{dried at 205 °} C. for 4 minutes. The MIT flex test (908 g load) gave 14,264 cycles and the coating on the fabric weighed 35.8 g / cm.

Example 13 '

5 * 4 kg of a solution of 75% titanium acetylacetonate in isopropanol and then 118.8 kg of distilled water were added to 10.8 kg of glacial acetic acid. 135 kg of aqueous polytetrafluoroethylene dispersion (60 $ polytetrafluoroethylene) were then added, followed by 16.2 kg of fluorinated acrylate dispersion from Example 8. The concentration of polytetrafluoroethylene in the dispersion obtained was 28.3% by weight . Heat cleaned glass cloth B was prepared using a customary in the textile industrial plant at a rate of 16.5 m / min, and then t by this dispersion through a wringer with a Quetschwalzenbelastung of 4 and passed through a heated at 315 ⁰ C oven. The dry weight of the coating obtained in this way on the fabric was 38.4 g / m ² . The MIT bending test (908 g) showed 23,457 cycles compared to 14 cycles for the glass fabric without the coating, 814 cycles for the same glass fabric with a known graphite / silicone coating and 677 cycles for the same glass fabric with a known polytetrafluoroethylene / Silicone coating.

Example 14

The glass fabric tested in this example was heat-cleaned glass fabric C with an MIT flexural test of 10 Cyden a load of 908g. A titanate solution was made by adding 16 parts of methyl ethyl ketone to 8 parts of a 75% strength solution of titanium acetylacetonate in isopropanol and 76 parts of distilled water were added dropwise.

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In an experiment, the glass fabric was immersed in the titanate solution (further diluted with water in order to achieve the coating weight given below) and then passed through a wringing device and dried at 260 ^° C. for 5 minutes. The titania polymer coating weighed 1.4 g / m and the MIT flex test gave 48 cycles.

In a further experiment, the glass fabric was converted into an aqueous one Polytetrafluoroethylene dispersion which was diluted with so much water that a coating weight after drying of about

30 g / m 2 was obtained, immersed. The MIT flex test gave 2000 cycles for this fabric.

In a further experiment 100 g of the titanate solution were diluted with 300 g of distilled water, and the diluted solution was added to 100 g of an aqueous polytetrafluoroethylene dispersion (60% polytetrafluoroethylene). The glass fabric was immersed in the dispersion, passed through a wringing device and ^{dried at 260 °} C. for 5 minutes. The resulting coating weighed 30 g / m 2 and the MIT flex test gave 9,000 cycles and, after treatment with acid vapor, 11,000 cycles. This corresponds to a more than 5-fold improvement in the flexural strength compared to the results described in the previous section, in which the coating on the glass fabric consisted only of polytetrafluoroethylene.

In a further experiment, the titanate solution was further diluted with 100 g of distilled water, and the glass fabric was immersed in this solution, passed through a wringer and dried at 260 ° C. for 5 minutes. This provided with a coating of glass fabric was then dipped in an aqueous PoIytetrafluoräthylendispersion, which was diluted with VJasser to a PoIytetrafluoräthylenkonzentration of 12 ^, passed through a wringer, and dried for 5 minutes at 260 ⁰ C. The coating obtained had a weight of 30 g / m 2

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The MIT-3ie test of the tissue obtained resulted in 10,000 cycles, and the bending strength increased after treatment with acid vapor to 24,000 cycles.

In the following Examples 15 to 18, heat-cleaned glass cloth A was used. The glass fabric was immersed in the aqueous polytetrafluoroethylene dispersion for about 1 minute. The coated glass fabric was passed through a wringer (no pressure) to squeeze off excess liquid and the coated fabric was dried in an oven at 204 ° C for about 4 minutes. The test patterns in the MIT Folding Endurance Tester strain was 1016 g, and the MIT bending test was carried out at a constant temperature of 2JJ + 1 ⁰ C and at a constant relative humidity of 50 + 5 $. Under these conditions, the MIT bending test on the heat-cleaned fabric without a coating showed a flexural strength of less than 100 cycles and on the heat-cleaned fabric with a coating of only polytetrafluoroethylene 2200 cycles. This value drops to only about 16O cycles on heat aging.

Example 15

The polytetrafluoroethylene concentration of the aqueous dispersion used in this example was about 26% by weight , and about 1/12 of the weight of the polytetrafluoroethylene present in titanium lactate was added to the dispersion. The fabric sample had before application of the coating a weight of 17, 6 g, and after application of the coating a weight of 19 g * 7 * which corresponds to a

Weight of the coating of 24 g / m. The MIT bending test of the glass fabric obtained showed a bending strength of 3850 cycles.

In another experiment, the titanium lactate concentration was increased until the ratio of polytetrafluoroethylene to titanium lactate in the dispersion was about 4: 1. The MIT bending test of the

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Glass fabric with the coating from this dispersion gave 2036 Cyclen and after heat aging 1355 cycles, i.e. the behavior in heat aging was better than that of the fabric obtained according to the previous paragraph.

Example 16

An aqueous polytetrafluoroethylene dispersion was about 8 # of the weight of the polytetrafluoroethylene in anhydrous fuming stannous chloride added in aqueous solution so that the polytetrafluoroethylene concentration in the dispersion obtained Was $ 26 wt. The glass fabric covered with this mass gave 1026 cycles before heat aging in the MIT bending test and 1309 cycles after aging.

Example 17

To 26.1 g of glacial acetic acid was ₇ K in propanol was added 13.1 g of 1,75m Zr (Q) C-Ji, whereby a clear solution was obtained. 162.7 g of water were slowly added to this solution, a slightly cloudy mixture being obtained. 131 * 8 g of aqueous polytetrafluoroethylene dispersion (60 wt .- ^ polytetrafluoroethylene in the dispersion) were added to this mixture. The weight of the glass fabric before application of the coating was 18.5 g and after application of the coating 20.8 g, corresponding to a coating weight of 24 g / m 2. The glass fabric provided with the coating made from this mass gave 6700 cycles before heat aging and 854 cycles after heat aging in the MIT bending test.

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With long-term use, filter bags made of glass fabric have become with a coating according to the invention can be used for longer proven to be filter bags with a well-known graphite / silicone coating. For example, was a glass fabric Type 63Ο and the coating compound specified below are used :

¹ I, 2 wt. JS aqueous titanium lactate solution (50 % solids)

7.2 wt. added water

71.5 wt. aqueous polytetrafluoroethylene dispersion (60% polytetrafluoroethylene, 3.6 % Triton X-100 as surface-active agent, based on the dispersion)

17.0 wt. Fluorinated acrylate dispersion of Example 8

The weight of the dried coating on the fabric was about 50 g / m. Filter bags from the one provided with the cover Fabrics had a lifespan of 11 months in a bag house for filtering soot out of one Airflow and the test will continue. In contrast, filter bags made of glass fabric with a well-known graphite / Silicone coating with this type of use presumably has a lifespan of about 6 months.

A long service life was also achieved in semi-technical systems with the following dimensions:

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k, k weight-JS aqueous solution of titanium lactate

(50 % pesticides) 4.6 wt. added water

73.2 wt. aqueous polytetrafluoroethylene dis-

persion (60 % polytetrafluoroethylene, 3.6 % Triton X-100, based on the dispersion)

17.8 wt. aqueous dispersion of fluorinated acrylate polymer, 6.75 % polymer solids.

- U ₃ -5 0'9 8 U? I 0 9 3 8

Claims (3)

Claims 2. Glass fabric according to claim 1, characterized in that the polytetrafluoroethylene and the condensation product are their own Form layers, with the condensation product being the base coat on the glass fabric and the polytetrafluoroethylene Forms top coat. 3. Glass fabric according to claim 1, characterized in that the coating consists of a mixture of components (a) and (b) consists. ¹ I. A method for producing a glass fabric according to claims 1 to 3, characterized in that a coating of a condensation product of a polyhydrolyzable compound of tetravalent titanium, zirconium or tin and then a top coating of polytetrafluoroethylene with a specific "melt viscosity of at least 1 χ 10 ^ poise at 38O ⁰ C. 0 9 8 L 7 I 1] 9 3 8 AD-i | 6l3r-Div. Process for the production of a glass fabric according to claims 1 to 3, characterized in that a coating of an aqueous dispersion of polytetrafluoroethylene with a specific melt viscosity of at least 1 χ ICr poise at 38O ⁰ C is applied to the fabric, the dispersion being a polyhydrolyzable compound des tetravalent titanium, zirconium or tin, the coating dries in the heat and condenses, whereby the heating is not so intense that sintering of the polytetrafluoroethylene is effected. - 2 5098A7 / 0938